Elamipretide

• Barth syndrome in patients weighing at least 30 kg (66 pounds), under FDA accelerated approval

Elamipretide (Forzinity) is a small peptide designed to protect mitochondria, the energy-producing structures inside cells. Researchers and online sellers call it SS-31, the name it carried in early studies. In September 2025, FDA granted it accelerated approval as the first treatment for Barth syndrome, a rare inherited disease that weakens the heart and skeletal muscles. It is not approved for any other use, even though "SS-31" is widely marketed for energy, longevity and athletic recovery.

What Barth Syndrome Is

Barth syndrome is a rare genetic disorder caused by changes in the TAZ gene, which is needed to make cardiolipin, a fat that holds the inner mitochondrial membrane together. It mostly affects boys and men, because the gene is on the X chromosome. Common features include cardiomyopathy, low white blood cell counts with frequent infections, muscle weakness, exercise intolerance, fatigue and slow growth. MedlinePlus Genetics estimates it affects about 1 in 300,000 to 400,000 people.

Care is usually led by a metabolic or genetics specialist together with cardiology. Primary care helps with vaccines, infection plans, nutrition and coordinating the many medications these patients take.

How Elamipretide Works

Elamipretide is a four-amino-acid peptide that crosses cell membranes and concentrates in the inner membrane of mitochondria. There it binds cardiolipin, the very molecule that is defective in Barth syndrome. Binding is thought to stabilize the membrane, help the energy-producing protein complexes work together, and reduce the leak of damaging reactive oxygen molecules.

In plain terms, the drug aims to make cells' power plants run more efficiently. That idea is why SS-31 attracted attention for aging and heart failure, but laboratory promise has not translated into proven benefit for those uses.

FDA Approval and the Evidence

The approval was based on the TAZPOWER trial, a small randomized, placebo-controlled study, and its open-label extension. Patients on elamipretide showed improved knee extensor muscle strength. FDA judged that this improvement is reasonably likely to predict real-world benefit, such as standing up more easily or walking farther, which is the standard for accelerated approval.

What Accelerated Approval Means

Accelerated approval lets FDA approve a drug for a serious disease based on a measurement expected to predict benefit, before that benefit is fully proven. The manufacturer must complete a randomized, double-blind confirmatory trial. The Forzinity label states that continued approval may depend on that trial confirming clinical benefit. If it does not, FDA can withdraw the approval.

Research Beyond Barth Syndrome

Elamipretide has been studied in primary mitochondrial myopathy, heart failure and dry age-related macular degeneration. A large phase 3 trial in primary mitochondrial myopathy did not meet its main goals. None of these are approved uses, and the results do not support using SS-31 for general energy or anti-aging. Our peptide therapy guide covers how FDA-approved peptides differ from research peptides.

Dosing and Administration

For patients who weigh at least 30 kg (about 66 pounds), the recommended dose is 40 mg injected under the skin once daily, at about the same time each day. A missed dose is skipped rather than doubled. People with severe kidney impairment receive a lower dose. Injection sites are rotated, since repeated injection reactions are the main problem with daily use.

Side Effects and Safety

Injection site reactions are by far the most common side effect: redness, itching, pain, bruising and firm lumps under the skin. They are usually mild to moderate but can lead some people to stop treatment. Allergic reactions are possible.

The vial contains benzyl alcohol, which has caused serious and fatal reactions in newborns and premature infants, so the product is not used in that age group. Because Barth syndrome itself causes low white blood cell counts, any fever needs prompt attention regardless of the medication.

Why "Research" SS-31 Is Not the Same

Vials sold online as SS-31 "for research use only" are not Forzinity. They are not made under FDA manufacturing standards, and their content, purity and sterility are not verified. Injecting an unverified product carries a risk of infection and of receiving the wrong dose or the wrong substance. We discourage using research peptides and are glad to review any product you are considering.

Everyday Care Alongside Elamipretide

Elamipretide is one part of a broader care plan, and the basics of Barth syndrome care still matter.

Infections and Fever

Many people with Barth syndrome have neutropenia, a low count of the white blood cells that fight bacteria, which can come and go. Families usually carry a written fever plan from their specialist. A fever should be treated as urgent, with a same-day call and often a blood count, rather than watched at home. Some patients take a medicine that raises white blood cell counts.

Vaccines and Prevention

Routine vaccines, including the yearly flu shot and age-appropriate COVID-19 and pneumococcal vaccines, help prevent infections that can hit harder when white cell counts are low. Dental care and prompt treatment of skin wounds reduce other infection risks.

Heart Monitoring, Nutrition and Activity

Regular echocardiograms and rhythm monitoring track cardiomyopathy, and heart failure medicines are adjusted as needed. Frequent meals and snacks help with low energy and low muscle mass, and many patients work with a dietitian. Gentle, regular physical activity within the limits set by cardiology supports strength. Elamipretide does not replace any of these steps.

Getting Care

Elamipretide is prescribed by specialists familiar with Barth syndrome. Our internists support these patients and their families with primary care, heart failure monitoring in coordination with cardiology, and medication review. To discuss a peptide you are taking or considering, schedule a visit.